The best anti-HIV treatment regimen for pregnant women is not known. Protease inhibitors (PIs) are often used, but they have side effects that may be harmful for pregnant women. It is not known if treatment regimens that do not include PIs are as effective in pregnant women as those that include PIs. This trial will compare two anti-HIV treatment plans, one with and one without PIs, in women who start HIV treatment during pregnancy. The study will evaluate the effects of the anti-HIV drugs on the developing infant and prevention of mother-to-child HIV transmission during pregnancy.